It is possible to identify nondiabetic persons who are at high risk of developing type 2 during the following several years. Identification can be done with simple clinical measures such as body mass index, plasma glucose concentrations, and HbA1c. People identified by glucose or HbA1c are said to have “pre-diabetes”, although these are not the only factors that can predict diabetes. Several randomized clinical trials have shown that weight loss interventions or several different drugs are effective in preventing or delaying the onset of diabetes in such high-risk persons. These findings lead to the questions of what people should be offered preventive interventions and what would be the benefits of offering them in clinical practice. One should aim not only for preventing or delaying the onset of diabetes, but also for delaying or preventing its vascular complications and other associated diseases such as cancer, extending healthy life span, and reducing health care costs. A major problem is that most of the evidence of benefit of preventive interventions is based on development of diabetes by biochemical criteria, such as increases in plasm a glucose fasting or during an oral g lucose tolerance test. There are limited data about the other potential benefits. The availability and gaps in such knowledge do not allow a clear answer of who should be given interventions and of what type for the prevention of type 2 diabetes.